This invention relates to a method of separating at least one organic substance having active hydrogen from a mixture of organic compounds which contains said one compound and other organic compounds which do not have active hydrogen.
Among the most important mixtures of the above type are the various tars such as bituminous coal tar, lignite tar, bituminous coal tar asphalt and the like. Tars usually contain mixtures of various organic compounds, including alkanes, olefins, aromatics, creosotes and the like which have active hydrogen, as well as organic compounds which do not have active hydrogen. The materials having active hydrogen are fairly toxic and may be carcinogenic and, as well, may contribute to the occurrence of undesired secondary reactions in the mixture. For example, crude tar will alter its properties in a short period of time even at low temperatures due to these secondary reactions.
It is known, of course, to separate individual substances or groups of substances from a tar mixture by means of fractional distillation or by solvent extraction.
When applying the distillation process, large amounts of distillation residues are formed in the tar, mostly on account of secondary reactions, and these residues can only be used for economical applications in extreme exceptions. They are therefore considered as operationally expensive wastes.
The cracking products arising from distillation also strongly affect the degree of purity of the distillation products obtained, which thereby suffer from very restricted applicability. Lastly, the distillation method requires much heat and therefore is costly.
Again, the extraction process too is beset with drawbacks. An appreciably amount of equipment is required on account of the large flow of solvents. This process furthermore is a great stress on the ecology.
In order to obtain clean individual substances, the groups of materials separated by extraction must be subjected to a further separation, thereby involving additional difficulties, extra procedures and equipment cost.
Similar conditions also apply to other homogeneous and heterogeneous mixtures of materials some of which contain active hydrogen.